What are you allowed to eat ( if anything ) whilst playing football ?

[My Pal is Worse Than Me.]

Say, a small snack of chicken & chips or
something similiar ?

[hard as nails]

Anything you like.
Obviously apart from banned substances.

Rio was eating packets of Jafa Cakes (and chucking the wrappers on the pitch) when he came back after his long ban for running away from the drug testers.

It's not against the rules to eat during a game.